Bicycle forks provide a means whereby the front wheel of a bicycle may be rotated relative to the bicycle frame and to allow for steering and control of the bicycle. Bicycle forks typically include a fork crown interconnected with a fork steerer tube rotatably mounted via bearings within a head tube of the bicycle frame. Two fork blades extend downwardly from opposing ends of the fork crown to provide securement of the crown to opposing sides of the axle of a front bicycle wheel. Rotation of the fork for steering is accomplished by rotating handlebars secured to the upper portion of the fork steerer tube.
Recently, bicycle forks have been designed which allow for absorption of load variations experienced by the front wheel of the bicycle caused by, for example, riding the bicycle over uneven terrain. One way of accomplishing such absorption is to provide fork blades which will shorten in length in response to application of an upward force on the bicycle wheel to which it is secured. For example, forks have been designed wherein each fork blade comprises inner and outer telescoping members compressible toward each other and expandable away from each other. Such forks typically include a means for biasing the telescoping members away from each other, such as by the use of coil springs, elastomers, and air springs. As uneven terrain and associated load variations are encountered by the front wheel, the telescoping members compress toward each other and the biasing means provides an increasing counteracting force to absorb the change in load and thereby at least partially prevent transfer thereof to the handlebars of the bicycle.
As noted above, elastomer members have been utilized to provide shock absorption for bicycle forks. For example, copending and commonly assigned U.S. Pat. application Ser. No. 08/116,683, filed Sep. 7, 1993, entitled "PRECISION SUSPENSION FORK FOR BICYCLES" and incorporated herein by reference, discloses a bicycle fork utilizing a plurality of elastomer members which are compressed upon compression of the telescoping members toward each other.
Under certain riding conditions such as while encountering extremely rough terrain, bicycle forks utilizing elastomers may rebound (i.e., expand) too rapidly after application and removal of a force to the fork (e.g., after hitting a large bump). Such sudden expansion of the telescoping members can result in an undesirable "clunking" noise and may further adversely affect the structural integrity of the fork over a long period of time. Such sudden expansion may also adversely affect the handling characteristics of the bicycle.
Accordingly, it is an object of the present invention to provide an elastomer-based suspension system for a bicycle fork, wherein the sudden rebound (i.e., expansion) of the telescoping members upon application and removal of a sudden force to the fork is damped. It is a related object of the present invention to provide rebound damping to an elastomer-based bicycle fork, wherein the rebound damping is adjustable. It is yet another related object of the present invention to provide such a bicycle fork having both rebound and compression damping with the amount of the rebound damping being greater than the amount of compression damping.